| OCR Text |
Show 366 DR. ST. GEORGE MIVART ON THE SKELETON OF [May 7, The lateral surface of the prosopium in front of a vertical line descending ventrad from the preaxial margin of each nostril is in P. erithacus slightly swollen and convex antero-posteriorly and rather more so dorso-ventrally. It is slightly more convex in both directions in L. flavopalliatus, in which also the more posterior portion of the side of the beak is less flattened than in P. erithacus. The ventral margin of the prosopium is, as already implied, more sharply curved in front of the tooth. The tooth itself is thus slightly more prominent, and the tomial margin behind it is slightly more convex than in P. erithacus. Postaxially the tomial margin ends in what may be called the jugal process (jp). It is broader and more rounded from within outwards, while above it the concavity which receives the preaxial end of the zygoma into it is much more marked in L. flavopalliatus. The jugal process itself extends relatively more postaxiad and somewhat more ventrad than in P. erithacus, so that the tomial margin presents a slight concavity towards its postaxial end, though very much less than that formed by the tooth and the parts in front of it. The upper boundary of this concave margin (which is the dorsal margin of the fossa for the zygoma) forms a suprajugalar (sj) process much like that of P. erithacus; but while in the latter species the postaxial margin of the beak above the suprajugalar process is postaxially concave and terminates dorsally in a small but distinct lachrymal process (Ip)-which is received into the frontal beneath a slightly marked prominent nasal process (np) of the latter bone-in L. flavopalliatus the postaxial margin above the suprajugalar process is nearly straight, and ends in a very minute lachrymal process, which more absolutely coincides with the dorsal line of the cranium in this external view of the skull than in the other species. In the latter, the lamina of bone which intervenes between the apex of the lachrymal process and the nearest point in the postaxial margin of the nostril is about as broad as two-thirds the antero-posterior extent of the nostril, but in L. flavopalliatus it is slightly less than half this extent. The depth of the lamina of bone ventrad of the nostril to the tomial border is one-fourth less than twice the diameter of the nostril. In P. erithacus it is only one-fifth less. T H E D O R S A L ASPECT of the prosopium has the outline of an isosceles triangle, the apical angle whereof is of about 50° instead of 40°, as in P. erithacus. Its base (the preaxial boundary of the cranio-facial articulation) is straighter and does not so clearly exhibit the curves (a very slight median concavity with two slight convexities external to it, external to which, again, are two concavities each bounded externally by one of the lachrymal processes) which there exist in P. erithacus. The lachrymal processes are relatively as well as absolutely smaller, and instead of projecting strongly outwards as well as backwards project backwards and but very slightly outwards, |
